High temperature lubricant



Patented Aug. 22, 1944 HIGH TEMPERATURE LUBRICANT Donald L. Wright, Westfleld, N. J., assignor, by mesne assignments,'to Jasco, Incorporated, a

corporation of Louisiana No Drawing. Application November 22, 1940,

Serial No. 366,714

14 Claims. (01. 252-29 This invention relates to a lubricating com position and to methods of lubrication, and more particularly to those suitable at high temperatures, especially at temperatures high enough "to cause charring or varnish and tar formation with the lubricating oil compositions used heretofore.

One object of the invention is the lubrication of devices such as oven conveyor chains, wheel bearings of kiln cars, annealing oven cars, ejector pins and other hot moving parts of die-casting machines, etc., which are required to operate at extremely high temperatures, i. e., above about 400 F., as, for instance, 500 F., 1,000 F., 'or higher. When conventional lubricating oils or greases are subjected to such hot operating conditions, decomposition of the petroleumingredient eventually occurs, with the formation of end products which are hard, abrasive, carbonaceous or coke-like materials which reduce clearance between rubbing members and tend to promote wear.

Broadly, this invention comprises a method lighter hydrocarbon vehicles such as refined kerosene or naphtha. A suitable material which A is available commercially contains about 10% of colloidal graphite and 90% of a light lubricating oil such as indicated above. I

The low boiling solvent, preferably a hydrocarbon oil, which constitutes the major proportion (usually more than.60%) oi the lubricant of this invention, should be below the lubricating oil boiling range. It may be a mineral seal oil which has a boiling range of about 510 to 670,F. or a kerosene which has a boiling range of about 375 to 510 F., or various refined naphtha-s, e. g.,

' those having boiling ranges such as from 300 of lubricating metal surfaces which in the ab-- sence of a lubricant would move in contact with each other at temperatures above about 400 F., by applying to said contacting surfaces 'a lubricant comprising a major proportion of a volatile solvent such as a light hydrocarbon oil, having a final boiling point below 750 F. and having a viscosity below about 45 seconds Saybolt at 100 F., said oilcontaining dissolved therein a M thickener such as a viscosity-increasing saturated linear aliphatic, preferably hydrocarbon 'polymerhaving a molecular weight above about 800 and having the property, when heated to preferred substance being colloidalgraphite, be-

cause it is substantially pure, i. e., containing not more than about 0.02% of ash. This colloidal graphite is preferably added in the form of a suspension in a light hydrocarbon liquid such as, a light lubricating oil having a Saybolt viscosity to380 F., 220 to 310 F., 160 to 230 F., or even still lower boiling such as 140 to 210 F. The primary purpose of using such a low-boiling oil is that it eva orates at high temperature without formation of varnish or tar, or eventual carbonization.

V The viscosity-increasing, linear aliphatic polymer should preferably be a high molecular weight, linear type, substantially saturated poly-' mer of an unsaturated aliphatic hydrocarbon, which polymer, upon heating, depolymerizes without ,carbonization or tar formation. As this constituent, it is preferred to use a polyisobutylene having an average molecular weight above 800 and preferably above 2,000, and for many applications of the invention it is preferred to use a still higher molecular weight polymer such as the plastic solid type having a molecular weight above 30,000, e. g., 60,000, 80,000, 100,000, etc. Other polymerized iso-olefins having similar characteristics may be used, for instance, polymerized isoamylenes, e. g., polymerized methyl Z-butene-l, etc. The amount of such polymer to be used will depend upon a number of factors such as the molecular weight of the polymer, the desired viscosity of the finished lubricant and the conditions under which the I lubricant is to be used.

of about to seconds at 100 F., or even a Inasmuch as the thickening effect of the polymer is directly proportional to the molecular weight, a solution having any desired viscosity can be prepared by usinga large amount of low lubricating life is desired, to use a polymer in the lower range mentioned; whereas for other purposes it may be desirable, i. e., where a short lubricating life is suificient, perhaps because the supply may be renewed frequently and easily,-to use a polymer within the higher range of molecular weight. Some examples are: (a) a 20%-solution of polyisobutylene having a molecular weight of 5,000; (b) a 2%-solution of polyisobutylene having a molecular weight of 150,000; (c) a solution of polyisobutylene having a molecular weight of about 60,000. Under some circumstances it may be desirable to use a mixture of low, medium, or high molecular weight,-as for instance a mineral seal oil containing dissolved therein 2% of polyisobutylene having an average molecular weight of about 150,000 (in order to get a large increase in viscosity with a small amount of addition agent, even though the breakdown in molecular weight of this polymer may be fairly rapid), and also containing dissolved therein about by weight of a polyisobutylene having an average molecular weight of about 5,000, which, owingto the relatively greater heat stability of this polymer, will extend the life of this lubricating composition over a longer period of time at the high temperature involved.

.In carrying out the invention, it is apparent from the above discussion of polymers of various molecular'weights, that the amount of the poly- ".mer to be usedmay vary overa fairly wide range (from 0.1% to 20%, or even more). If colloidal graphite or other solid lubricant is added, the amount thereof to be used should ordinarily be about".05-2;0%' by Weight based 'on the total lubricating-composition; preferably the amount of graphite should be about 0.1-0.3%. If the col- .loidal graphite is added inthe form of a suspension ima-lightoil, as for instance a 10% suspension'in oil, the amount of the suspension to be used will be about Oil-20.0%.

Instead of polyisobutylene, one may use other :at temperatures below 0 C., e. g. '70 C., -80 0.,

Crafts halide dissolved in an alkyl halide solvent, e. g., A1013 in methyl chloride, and preferably in the presence of liquified propane, ethane, ethylene or other inert gas as refrigerant-diluent. Another suitable thickener is the oil-soluble, substantially saturated i'sobutylene-ethylene copoly- 'mer made at 100-400" C., usinghigh pressure, e. g., 500, 1,000, or 2,000 atmospheres, preferably with addition of a small amount of oxygen.

If desired, small amounts of other addition agents may be added to the lubricating composition, as for instance 0.1 to 2 or 3% of an ester, as for example the low'molecular weight alkyl ester of a' fatty acid, having the property of increasetc. using-'as catalyst a solution' of a Friedelingthe oiliness or lubricity of the composition.

Small amounts of other materials such as oxidation inhibitors, depolymerization inhibitors, ex-

Table I Percent comp.Test No.

Polybutene 7. 5 4. 3 i5 1. 7 7. 0 Colloidal graphite suspension 5. 0 2.0 3 2. 0 2. 0 Ester 1.0 1.0 1.0 Mineral seal oi1.. 86. 5 02. 7 82 06. 3 80.1 1, 000 800 600 550 500 Oil can x r x Oil cup Mechanical lubricstor All of the above compositions were found satisfactory, some of them being used for the lubrication of annealing oven car wheel bearings, oven conveyor chains, and kiln car roller bearings, bearings of motor-gear sets subiectedto radiiint heat of hot metal (as hot as 1100 F.) and bearings of elevators and conveyors handling hot coke.

In these various industrial uses, great difllculty had previously been experienced in lubricating the equipment but the compositions of this invention gaveexcellent results. In a number of cases, after use for a considerable time with these new lubricating compositions, the equipment was disassembled in order to examine the bearings, and invariably the latter showed no signs of carbonaceous deposits and only a thin film of colloidal graphite. tage of this invention is illustrated in the case of test No. 4 where the annealing oven conveyor now rolls readily by gravity, whereas formerly using lubricants consisting-entirely of miners! seal oil and polybutene, i. e., withoutan'y colloidal graphite or other noncombustible solid material. Typical of such applications are the lubrication of oven conveyor bearings operating at 420 1"., with oil cup application where a blend of 15% polybutene, 85% mineral seal oil was utilized; the same lubricant successfully operated on electiic motor bearings at temperatures so high that it had previously been impossible to keep even high temperature soda base greases in the bearing housing. other moving but parts of die-casting machines has been most successful with a blend of 7.5% polybutene, 1% ester, 91.5%' mineral seal oil. All of these applications are being much more successfully lubricated than with any other previously used lubricants, and show that for certain types of uses the graphite not only may be, but should be, omitted from the composition.

Since the viscosity of the solution of polymer in mineral seal oil is an important factor in obtaining the proper feeding of the lubricant to suit the various types of lubrication means, used in industry, such as referred to at the bottom of the above table, or even by hand where a thick plastic lubricant is'used, the following table is given in order to show the effect of the percentage used, on theviscosity of the'mineral of polymer An additional practical advsn- Lubrication of ejector pins and l Viscosity (seconds Saybolt at 100 F.) of mineral seal oil solution Percent of polybutene l i 7 4o 1 a 100 1 Plastic mass Must be hand-packed.

The amount of mineral seal oil used in Table'II was inall cases 100% minus theamount of polyvbutane used. The mineral seal oil itself had a flashpoint of 260'270 F. and a Sayboltviscosity of about 40 seconds at 100 F. A still fu'rther advantage of ,the present invention is that these new lubricants do not run or spread appreciably at the high operating temperatures involved. Their superiority in this respect over prior art lubricants is readily demonstrated by the following simple tests; v Test A.-A refined petroleum lubricating oil fraction having a, viscosity of exactlylOO seconds Saybolt at 100 F. when dropped onto a hot metal surface (having a temperature of 400 F. or higher) having an area of about 8 inches by 10 inches will require only about 1012 drops to spread over the entire surface.

Test B.-A solution of 60,000 molecular weight 'polybutene injmi'neral seal oil having a Colleen tration suflicient to make a solution having exactly the same viscosity, namely, 100 seconds Saybolt at 100 F.,- when dropped onto the same type of hot metal surface in the same quantity, i. e., about 10-12 drops, will cover only about 1 square'inch of surface. In other words, in round figures, the plain mineral oil spreads over about '50 to 100 times as g-reatan area as the mineral seal oil solution of polybutene having the same viscosity. This means that the polybutene solution forms correspondingly a 50- to 100-times thicker layer or film of lubricant on the hot metal surface, and, consequently, these polybutene solutions do not'run out of the bearings like the plain minerallubricating oils of the corresponding viscosity. Furthermore, this advantage of greater thickness of lubricant film becomes even greater when more viscous oils and solutions are compared, for instance,'those having a. viscosity of 300 seconds or 1,000 seconds Saybolt at 100 F.

Althoughthe theory of the mechanism of the operation of the invention is not entirely understood, it isbelieved to depend partly upon the use of an operating temperature sufficiently high to cause at least partial depolymerization of the polymer. Conversely, it is believed that the polymer or thickening agent should be one which decomposes, by depolymerization or otherwise, when subjected to operating temperatures involved, and does so without leaving any substantial amount of carbonaceous residue. Furthermore, the mineral seal oil or other even more volatile solvent which appears to be necessary primarily as a vehicle or fluid medium for getting the polymer, alone or with the graphite, into place in the bearing, should be a liquid which evaporates under the operating temperatures involved, without leaving any carbonaceous, varnish-like adapted to be decomposed or tarry residue, which would either undesirably increase the resistance of the moving metal parts or would'cause harmful abrasion thereof. v

, Itis not inten'ded that the invention be limited toany of the materials which have been mentioned merely asspecific examples norby the specific proportions given for the sake o'f'illustration,nor by any theory as to the mechanism 'of the invention, but only by theappended claims in which it is intended to'claim all novelty inherent-in the invention as broadlyas the, prior art permits. I claim: I V ,f l'. The method of lubricating hot metallsurfaces which,'in the absence of a lubricant, would m0ve incontact with each other, at temperatures abov about 400 F., which comprises applying to said moving metal parts a lubricant compris-' ing'a major proportion of a volatile solvent'hav; ing afinal boiling point below 750 F.',, having ja viscosity below 45 seconds Saybolt at 100?; :F. and capable of evaporating at suchihigh .liflm peratures without. leaving any harmful residue, said lubricant also containing a sufilcient amount of, an oil soluble organic thickener comprising essentially a saturated. linear aliphatic polymer having a molecular weight above about 800, at such high "tern; peratures' without leaving any substantially harmful residue, to make @a solution havin -a viscosity of at least 100 seconds Saybolt"atj100 F., the product of the percent of polymer itimes the molecular weight of the polymer being at least 100,000.. l i

2. The method of lubricating hot metal, surfaces which, in the absence of a lubricant, would move in contact with each other, at tempera-j tures above about 400 F., which comprises applying to said moving metal parts alubricant comprising a major proportion of a volatile hydrocarbon oil having a final boiling point below about 675 F. and having a viscosity below about seconds Saybolt at 100 F. and capable of evaporating at such high temperatures without leaving any harmful residue, saidlub'ricant also containing dissolved therein a thickener corn-j prising essentially a saturated hydrocarbon polymer having a molecular weight above 800 adapted to be decomposed at such high temperatures without leaving any substantially harmful resi due and having the property of greatly'reducing the spreading tendency of the volatile solvent,

the amount of said thickener being sufficient to make a solution having a viscosity of at least 100 seconds Saybolt at F. the product of the per cent of polymer times the molecular weight of the polymer being at least 100,000.

3. The method of lubricating metal surfaces at a temperature above 400 F. which comprises applying to said moving metal parts a lubricant consisting essentially of mineral seal oil and polyisobutylene, the amount of said polyisobutylene being suflicient to make a solution having a viscosity of at least about 100 seconds Saybolt at 100 F.

4. The method of lubricating metal surfaces at temperatures above about 400 F. which comprises applying to said moving metal parts a lubricant comprising a major proportion of a hydrocarbon oil having a final boiling point below about 675 F. and having a viscosity below about 45 seconds Saybolt at 100 F., said lubricant also containing dissolved therein a suffi- ,eient amount of a saturated hydrocarbon polymer having a molecular weight above 800 to make a hydrocarbon solution having a viscosity above 100 seconds Saybolt-at 100 F., the product of the per cent of polymer times the molecular weight of the polymer being at least 100,000,

and said lubricant also containing a small amount of a non-abrasive solid lubricant which is noncombustible at temperatures up to about 2500" F.

5. The method of lubricating hot metal surfaces which, in the absence of a lubricant, would move in contact with each other at temperabutylene having a molecular weight above 800,

the amount ,Qof. said polymer being suflicient to make a mineral oil solution having a viscosity of atflleast 100 seconds Saybolt at 100 F., the

product of the 'p rcent of polymer times the molecular weight of the polymer being at least 100,000, fsaid lubricant also containing about .05% to'2'.0,% ofcolloidalgraphite.

high temperature .lubri cant for use at temperatures above about 4005K, comprising a major proportion or a-volatile solvent having a final boiling pointIbeIoW 750 F. and capable of evaporating at saidhigh temperatures withciut'leaving. an undesirable residue, said lubricant also containing 'a suificient amount of thickenercoinprising essentially a saturated linear aliphatic. polymer havinga molecular weight abov'ej ab'out,. 800, soluble in said solvent and capableof'decomposing at said high temperatures without leaving any substantial harmful residue, to make a solution having a viscosity of at least 100 seconds Saybolt at 100 F. the product offthe. per cent or polymer times the molecular weight of the polymer being at least 100,000, and also containing, a .small amount of a comminuted, non-abrasive'vsolld lubricant which is non-combustible at temperatures up to about 2500" F.

.7, A high temperature lubricant for lubrication of moving metal parts attemperatures above about .400" .F., which comprises at 1east 60% by. Weight of mineral seal oil, about 01-20% of polyisobutylene having a molecular weight abete about 800, the amount of said polymer be ing sufficient to make a mineral oil solution having a viscosity of at least 100 seconds Saybolt at 100 F., the product of the per cent of polymer times the molecular weight of the polymer being at least 100,000, said lubricant also. containing about .05%-2.0% of colloidal graphite.

8..A high temperature lubricant for use at temperatures aboveabout 400 F. consisting essentially of. a major proportion of mineral seal oil and a minor proportion of polyisobutylene having an average molecular weight above about 800, the amount of said polyisobutylene being suificient to make a solution having a viscosity of at least about 100 seconds Saybolt at 100 F. 9. A high temperature lubricant for use at temperatures above about 400 F., consisting esmer times the molecular weight of the polymer Y is at least 100,000.

11. A high temperature lubricant for use at temperatures above about 400 F., consisting essentially of about 82 to 96% by weight of mineral seal oil and about 2 to 15% by weight of polyisobutylene having a molecular weight of about 60,000. 7

l2. Lubricant according to claim 11 also con taining about 2 to 5% by weight of acolloidal graphite suspension comprising essentially about 10% by weight of graphite and about by weight of a light lubricating oil.

13. A high temperature lubricant for use at temperatures above about 400 F., comprising at least 60% of a volatile solvent having a final boiling point below 750 F., a flash point of at least 260 F., a viscosity below about 45 seconds Saybolt at 100 F., and capable of evaporating at said high' temperatures without leaving an undesirable residue, said lubricant also containing dissolved therein an oil-soluble saturated linear aliphatic polymer serving as thickener, having a molecular weight above 800 and capable of decomposing at said high temperatures without leaving any substantial harmful residues, in amounts sufilcient to make a solution having a viscosity of at least 100 seconds Saybolt at 100 F., the arithmetic-product of the per cent of polymer times the molecular weight of polymer being at least 100,000, and said total composition being capable of being heated to temperatures above 400 F. to complete dryness without leaving an undesirable residue.

14. A high temperature lubricant for use at elevated temperatures such as about 400 to 1000 ll, having a viscosity of at least 100 seconds Saybolt at 100 FE, consisting essentially of mineral as oil containing about .05-2.0% of colloidal graphite and about 2 to 25% byweight of a linear substantially saturated aliphatic hydrocarbon polymer having a molecular weight above about 30,000.

DONALD L. wnrorr'r'. 

